The invention described later in detail relates to distributed data access systems with a plurality of computers that afford database access to a group of geographically distributed users. More particularly, the invention concerns a distributed data access system having a plurality of computers with 1-for-N redundancy in which one of the computers is operated on a standby basis, ready to assume operation of any of the other computers in the event of failure in that computer.
The invention operates in a system that provides a variety of financial data services to subscribers through terminals that access a financial information database. In a prior system, trading information from various stock exchanges, news information from news services, and other information from private databases was transmitted over conventional means to each of a plurality of regional communication centers (RCC). The RCC's were geographically distributed throughout the United States, each serving to assemble and archive securities trading information, news service information, and private database information, and to distribute archived information through one or more concentrators to local users within the geographical area served by the RCC. For example, Quotron Systems, Inc., the assignee of this application, has maintained a financial information distribution network (the "QSI" network) including seven regional communication centers and over 200 concentrators in 50 different locations, all serving 5,000 users through 80,000 desk units.
Each RCC included at least one computer facility referred to as a regional computer (RC). Each RC comprised at least five computers connected together by a high speed channel. Two computers in the RC performed communication services, while at least three computers were provided for file services. Some RC configurations included six computers in which two were communication servers and four were file servers. In order to meet reliability, availability, and speed requirements, each RC architecture embraced 1-for-1 redundancy for each computer in the RC. Thus, an RC with six computers needed 12 computers in order to satisfy the redundancy requirements. In the QSI network, there were 45 RC's.
In order to reduce significant overhead expenses, including communication, equipment, and network costs, a system architecture has been proposed to consolidate the seven RCC's of the QSI network into a single, national distribution center. In order to reduce the complexity and potential downtime involved in changing to a single, national center, the seven regional partitions were retained. In the national center, one or more of the RC's is implemented in a respective one of a plurality of computer facilities. Each replacement computer facility is referred to as an XRC. The significant technological challenge in establishing and operating the national center with over ten XRC's was to provide stability and reliability of the flow of information in the event of XRC failure.